Press release

New measurements over the Amazonian rainforest reveal link between the surface elevation and the emissions from plants

23 May 2017 - Researchers investigated the role of gases emitted by plants on atmosphere and climate in the Amazonian rainforest, the world’s most important ecosystem. Among these gases, isoprene plays a key role in atmospheric chemistry.

For the first time, the fluxes of isoprene were directly measured from aircraft in central Amazonia. The researchers discovered a surprising link between the fluxes and surface elevation in the forest. A team from the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) compared the observations with atmospheric models, which are constrained by satellite observations, and found similar results.

For this study, Belgium collaborated with the Universities of California, Harvard and Brazil. The results appeared in Nature Communications on May 23, 2017.

Terrestrial vegetation emits vast quantities of hydrocarbon to the atmosphere. These emissions form aerosols and other gases that have an impact on air quality and climate.

Modelled isoprene fluxes estimated by the tropospheric models of BIRA-IASB, based on satellite observations of formaldehyde.

Isoprene dominates global hydrocarbon emissions with tropical regions accounting for 80% of the total emission. The Amazon rainforest has the richest collection and abundance of vegetation species on Earth. But it is still not clear:

which plant species contribute most to the total isoprene flux

how these isoprene emitters are distributed across the Amazon basin

what is the magnitude of the emission

how it varies seasonally

This study reports the first isoprene emission estimates based on direct aircraft measurements over the central Amazon forest, in the area of Manaus. Our researchers compared them with independent estimations of isoprene emissions based on satellite observations of formaldehyde, a gas formed during the chemical oxidation of isoprene in the atmosphere.

Isoprene emissions as a function of altitude. In red, the direct measurements from the aircraft. In purple and blue, the isoprene emissions estimated using tropospheric models based on satellite observations of, respectively, GOME-2 and OMI sensors.

The satellite observations support this finding. They show similar correlations between the model estimations of isoprene and the topography. This suggests that the surface elevation in the landscape determines the distribution of plant species, thereby explaining a substantial part of the isoprene emission variability. This insight leads to significantly improved isoprene emission estimates.

The Belgian contribution to this study was supported by the Belgian Science Policy Office through the Programme of Space Application PRODEX-TROVA and the ESA project GlobEmission.